Pedal vehicles such as bicycles and tricycles provide an environmentally-friendly mode of transportation for short-distance commuters and have health benefits for users. In addition, use of such vehicles is not governed by the strict laws that apply to cars and motorcycles, rendering them usable by almost all members of the public. Tricycles have an advantage over bicycles in their inherent stability, and they are thus easier to operate by, for instance, the elderly and persons with disabilities. Moreover, tricycles may be adapted to carry considerable loads, further enhancing their utility.
For many individuals, the use of pedal vehicles is restricted to travelling short distances and/or routes without any substantial hills, because of the human energy required to power the vehicles. This is particularly true for tricycles, which are typically heavier than bicycles, and which may be carrying heavy loads. To extend the use of pedal tricycles to a wider range of situations and users, there have been numerous proposals for the provision of a motor to power, to varying degrees, the tricycle.
For example, U.S. Pat. No. 4,313,517 discloses a three-wheeled electric vehicle that can be powered by motor power or pedal power. The construction of this tricycle is such that the pedals are provided for emergency power for use when, for example, the batteries supplying power to the electric motor are discharged. The pedals are therefore not intended to be used to power the tricycle to any great extent.
A tricycle described in U.S. Pat. No. 4,183,418 employs an electric motor to drive the rear wheels via a slip clutch, as well as pedals, such that either or both may be used to power the vehicle. However, the patent does not teach the use of a clutch or ratchet in the pedal drive mechanism, suggesting that the pedals will always spin when the tricycle is in motion.
U.S. Pat. No. 4,111,274 teaches a tricycle having an electric motor directly linked to one rear wheel, and pedal power linked to the other rear wheel via a coaster brake assembly. Thus, although the pedals and motor may be used individually or simultaneously, the absence of a clutch between the motor and its associated rear wheel will cause the motor and its corresponding drive components to be driven during pedalling.
U.S. Pat. Nos. 3,827,519 and 3,759,339 each relate to a pedal/electric motor powered tricycle in which motor power may be engaged to the rear wheels through a clutch. While simultaneous use of both pedal and motor power is possible, there is no provision for releasing the connection between the rear wheels and the motor when the motor is on and the pedals are driving the tricycle faster than that which can be attained by the motor. In this case, the pedal power would disadvantageously also be turning the motor.
Finally, U.S. Pat. No. 3,598,195 describes a tricycle powered by electric motor and/or pedals, wherein the disadvantages of the tricycles discussed above are overcome by providing a ratchet between a differential on the rear axle and each of the two power sources. Nevertheless, this tricycle has a disadvantage in that coasting is inefficient because rotation of the rear wheels causes the differential to be driven. This disadvantage is also present in the above-described prior art tricycles which lack a clutch between the rear axle and the differential and/or motor.